Device for keeping a cold-rolled strip dry in the outlet of strip rolling mills

ABSTRACT

The preferred quality requirements postulated by producers for the product cold-rolled strip include, among good flatness and optimum thickness tolerances, also dryness of the strip in the outlet of strip rolling mills. Already existing devices that are disposed in the outlet of roll stands comprise stationarily installed and mobile partitions, a roll barrel and a roll strip venting device and a vapor escape. The aim of the invention is improve the aforementioned device by disposing above the rolled strip ( 10 ) a strip deflector ( 3 ) with an integrated fan-operated strip venting device ( 4 ) by means of a low-pressure nozzle ( 7 ) and an upper roll barrel gap seal ( 5 ) in the form of a slotted nozzle ( 6 ) and below the rolled strip ( 10 ) an extraction device ( 16 ) with integrated lower strip deflector ( 17 )

The invention concerns a device for keeping cold-rolled strip dry in theoutlet of strip rolling mills with means for deflecting liquid rollingmedia in the area of the strip outlet and/or for keeping away liquidspraying onto the surfaces of the strip, wherein these means, which may,for example, be combined into a functional unit, comprise permanentlyinstalled partitions and movable partitions located above and below therolled strip, a roll barrel blowing device, a roll barrel gap seal, anda vapor exhaust system.

The most desirable quality requirements of producers of the product“cold-rolled strip” include, besides good flatness and optimum thicknesstolerances, dryness of the strip in the outlet of cold-rolling mills andstrip mills in order to avoid surface defects, such as spots, in thefurther processing of the strip.

In the state of the art, different devices and measures are known whichhave the goal of obtaining dry strip that is free of moisture androlling media. To this end, blowing systems, partitions, exhaust systemsand combinations of these devices and measures are used in variouscases.

For example, DE 44 22 422 A1 describes a device for contact-free sealingof the gap between a partition and a work roll in the outlet of arolling stand, and a partitioning element with a slotted nozzle isarranged approximately tangentially to the surface of the work roll at arelatively short distance from it and from the rolled strip. On itsfront face, the partitioning element has an end part that tapers like ablade, is arranged approximately tangentially to the surface of the rolland a short distance from it, and is arranged and designed in such a waythat an injector-like flow channel that steadily expands in crosssection is formed between it and the surface of the roll.

Previously known devices and measures for producing dry strip areenergy-intensive, complicated, and cumbersome during both roll changesand adjustment of the roll gap, and create a disturbing noise level.

In some cases, sufficient removal of the unwanted moisture from thesurface of the strip and thus a dry cold-rolled strip that satisfiesrequirements were not achieved, because insufficient attention was paidto the reasons for the deposition and/or the entrainment of moisture onthe surface of the strip. These reasons include the following:

-   -   rolling medium is entrained by the rolls and thrown onto the        strip as it runs out;    -   rolling medium sprays beside the edge of the strip through the        roll gap and in this way gets back onto the strip; and    -   vapor in the outlet area of the mill condenses and drips onto        the strip.

To obtain cold-rolled strip that is truly free of interfering moisture,EP 0 765 696 B1 proposes a combination of various means for deflectingand removing liquid rolling medium. In this method, a stationarypartition, which has one part installed above the strip flow as far asthe stand platform and another part installed below the strip flow asfar as the base plate, partitions the moist/wet roll area from thefinish-rolled strip. An additional, movable partition that consists ofmoving parts provides more complete partitioning of the moist/wet rollarea from the finish-rolled strip, but at the same time, due to themobility of the parts, it allows an advantageous accessibility of therolls, for example, when a roll change is being carried out. At the sametime, these movable parts realize the function of a strip deflectorand/or a means for strip transfer. The moving parts, which are designedas stops, can be optionally adjusted to be mechanically stationary oradjusted as a function of roll barrel wear.

Other installed components are:

-   -   a roll barrel blowing device for preventing rolling medium that        has been squeezed off from being transferred to the        finish-rolled strip,    -   a roll barrel gap seal, which seals the moist/wet roll space        above the rolled strip from the finish-rolled strip,    -   a strip edge blowing device, by which the entrained rolling oil        at the side of the strip edge is carried away to the side from        the rolled strip, and    -   a vapor exhaust system in the strip channel with parallel        airflow in the direction opposite the direction of strip flow        above and below the rolled strip.

The objective of the invention is to further develop the device forkeeping cold-rolled strip dry that is described in EP 0 765 696 B1 andreferred to as a DS (dry strip) system to ensure that the rolled stripleaves this “DS system” drip-free and that only a residual amount ofoil, which is determined by the emulsion composition and the rollingprocess, still remains on the rolled strip.

In regard to a device of a rolling stand of the specified type forkeeping cold-rolled strip dry, which is installed above and below thestrip flow between the housing uprights and has the characterizingfeatures of Claim 1, this objective is achieved by

-   -   an upper strip deflector arranged above the rolled strip with        integrated fan-driven blowing by means of a low-pressure nozzle        and with an upper roll barrel gap seal in the form of a slotted        nozzle, and    -   a separate exhaust device arranged below the rolled strip with        an integrated lower strip deflector.

Advantageous modifications of the invention are specified in thedependent Claims.

With the system parts specified in Claim 1, the device consists alltogether, in the area of the strip outlet, of the following system partsthat work together:

-   -   stationary partition above and below the rolled strip;    -   upper strip blowing system with fan-driven low-pressure nozzle;    -   upper roll barrel blowing system;    -   upper roll barrel seal;    -   upper strip deflector with adjustment mechanism for holding the        blowing nozzle arranged above the rolled strip and for        supplementing the upper partition; and    -   strip channel with separate exhaust system below the rolled        strip and an integrated lower strip deflector.

The interaction of these individual components successfully prevents therolled strip from being recontaminated with rolling oil or emulsionafter leaving the rolling gap. Rolling oil or emulsion escaping to theside of the rolled strip through the roll gap is carried off to the sidein a well-defined way and removed from the outlet area by the lowerexhaust system. This ensures that the upper and lower sides of therolled strip leave the outlet area drip-free and that only a residualamount of oil, which is determined by the emulsion composition and therolling process, still remains on the rolled strip.

In detail, the following effects are achieved by the individualcomponents:

-   -   the stationary stand partition, which is installed above the        rolled strip as far as the stand platform and below the rolled        strip as far as the base plate, partitions the wet roller area        from the finish-rolled strip;    -   the upper strip blowing system with a fan-driven low-pressure        nozzle carries the emulsion escaping next to the rolled strip        through the roll gap to the side;    -   the upper roll barrel blowing system prevents squeezed-off        emulsion from running down on the roll and getting onto the        finished strip. The squeezed-off emulsion is carried away to the        side by the airflow;    -   the upper roll barrel seal in the form of a slotted nozzle that        exploits the Coanda effect, by which the air jet emerging from        the orifice of the slotted nozzle follows the curved surface of        the roll and thus produces, in the front area of the strip        deflector, contact-free sealing of the area above the strip        deflector from the roll and thus from the finish-rolled strip;    -   the upper strip deflector is designed to be moved at an angle of        20° to 45° and is arranged in such a way that the roll change        can be made without any difficulty;    -   the strip channel that is formed with a separate exhaust system        below the strip flow produces a well-defined flow around the        edge of the strip after the roll gap. The exhaust system can be        fan-driven from a suction tank installed below the strip, or        exhausting can be accomplished with the aid of injector nozzles,        which are installed below the strip flow in a strip guide table        in such a way that they can be turned on in zones. The strip        channel is formed in such a way that is can also be used as a        threading aid for the leading end of the strip.

Although optimum utilization of the components described above isachieved only when they work together functionally, they can also besuccessfully used as individual components, especially in rolling millsthat are already in operation.

Other details, advantages and features of the invention are explained ingreater detail below with reference to the embodiments illustrated inthe schematic drawings.

FIG. 1 shows a vertical partial section of a device for keepingcold-rolled strip dry.

FIG. 1 a shows an enlarged view of the roll barrel gap seal from FIG. 1.

FIG. 2 shows a vertical section of airflow paths of the exhaust air inan exhaust device.

FIG. 3 shows a top view of airflow paths after a low-pressure nozzle.

FIG. 1, in which the actual rolling stand is not included in thedrawing, shows two backup rolls 31, 32. Two work rolls 33, 34 with anadjustable roll gap 12 are positioned between the backup rolls. Aboveand below the rolled strip 10 running out of the rolling stand (fromleft to right in the drawing), there is a moist/wet rolling zone 11,which is formed by the rolls 31, 32, 33, 34 and the rolled strip 10 andfrom which the rolled strip 10 that has run out is to be shielded.

To this end, first, this moist/wet rolling zone 11 is already partiallypartitioned from the finish-rolled strip 10 by a stationary upperpartition 1 and a stationary lower partition 2. These stationarypartitions 1, 2 are supplemented by movable partitions.

Above the rolled strip 10, this supplementary device consists of anupper, movably designed strip deflector 3, which contains an integratedfan-driven strip blowing device 4 with a low-pressure nozzle 7. Thisstrip blowing device 4 is lengthened in the direction of the upper workroll 33 by a slotted nozzle 6 to form a roll barrel gap seal 5 andextends to a point very close to the work roll 33. Due to the specialdesign of the slotted nozzle 6, the remaining gap between the work rolland the slotted nozzle 6 is sealed by utilizing the “Coanda effect”. Inaccordance with the Coanda effect, the air jet emerging from the slottednozzle 6 follows the contour of the curved surface of the work roll 33positioned directly in front of the slotted nozzle 6 and thus pushesback the liquid media adhering to the surface of the roll. The enlargeddrawing in FIG. 1 a in particular clearly shows this slotted nozzle 6 ofthe roll barrel gap seal 5.

In addition to the slotted nozzle 6 (for work roll blowing) and thelow-pressure nozzle 7 (for strip blowing), a roll barrel blowing device9 is installed in the upper area of the work roll 33, by which liquidmedia still adhering to the work roll is driven off in the direction ofrotation of the work roll 33 and thus away from the rolled strip 10.

To supplement the stationary lower partition 2, an exhaust device 16 isinstalled below the rolled strip 10, whose forward end is lengthened bya lower strip deflector 17 that extends as far as the lower work roll34. The exhaust device is designed in such a way that, together with theupper strip deflector 3, it forms a strip channel 15, through which therolled strip 10 is guided and which can also be used as a threading aidfor the leading end of the rolled strip. The exhaust device 16 includesa suction tank 18 with a connected emulsion drain line 19 and an exhaustair line 20.

FIG. 2 shows a vertical section of the exhaust device 16 with theresulting directions of airflow 21. Air overpressure prevails above therolled strip 10, while the air exhaust produces a partial vacuum belowthe rolled strip. Above the rolled strip 10, the resulting airflow paths21 run parallel to the rolled strip to the edge of the rolled strip andthen down along the edge into the suction tank 18, where the air isdeflected towards the middle of the suction tank 18. The air is thenfurther conducted into the exhaust air lines 20, by which the exhaustair is removed from the system. The deflection of the airflow fromvertically downward (at the edge of the rolled strip) to horizontal(towards the middle of the suction tank) causes centrifugal separationof the droplets of emulsion or rolling oil, which are then collected inthe separation chamber 22, from which they are removed through theemulsion drain line 19. In FIG. 2, the rolled strip edge region 13,which is important for keeping the cold-rolled strip dry, is shownespecially prominently.

FIG. 3 shows the directions of airflow 14 of the fan-driven stripblowing device 4. The air leaves the low-pressure nozzle 7 broadlyfanned out in the opposite direction from the running direction of therolled strip and is then distributed symmetrically over the entire uppersurface 30 of the rolled strip towards the edges of the strip due to theplates 7′ of the low-pressure nozzle 7. The rolling oil emerging fromthe roll gap 12 with the rolled strip 10 is reliably forced to the sidetowards the edges of the strip in this way, from which it is conveyeddownward into the suction tank 18 by the air of the exhaust device 16flowing around the edges of the strip.

It is apparent that the essential feature of the invention is thecombination of all of the indicated structural elements of the devicefor keeping cold-rolled strip dry and their function in the new DSsystem. The device preferably can work together with a roll gaplubrication system that operates as a function of strip width and, inparticular, independently of axially displaceable or stationary rolls

The invention is not limited to the illustrated embodiment. Depending onrequirements, individual components and their combination with oneanother can be varied. In addition, however, the device should bedesigned in such a way that it reliably prevents moisture in the form ofdrops or vapor condensation from falling back onto the rolled strip 10and thus optimizes the quality of the strip. It is crucial to maintainthe design in accordance with the invention, and the forced airflows ofthe upper strip blowing device 4 and of the lower exhaust device 16, aswell as the overall interaction of the specified structural elements arealso crucial.

List of Reference Numbers

-   1, 2 stationary partitions-   3 upper strip deflector-   4 strip blowing device-   5 upper roll barrel gap seal-   6 slotted nozzle-   7 low-pressure nozzle-   7′ plates-   9 roll barrel blowing device-   10 rolled strip-   11 upper and lower rolling zone-   12 roll gap-   13 rolled strip edge region-   14 airflow direction of 7-   15 strip channel-   16 lower exhaust device-   17 lower strip deflector-   18 suction tank-   19 emulsion drain line-   20 exhaust air line-   21 airflow direction of 16-   22 separation chamber (for emulsion/rolling oil)-   30, 30′ surface of the rolled strip-   31, 32 backup rolls-   33, 34 work rolls

1. Device for keeping cold-rolled strip dry in the outlet of striprolling mills with means for deflecting liquid rolling media in the areaof the strip outlet and/or for keeping away liquid spraying onto thesurfaces (30, 30′) of the strip, wherein these means, which may becombined into a functional unit, comprise permanently installedpartitions (1, 2) and movable partitions located above and below therolled strip (10), a roll barrel blowing device, a roll barrel gap sealand a vapor exhaust system, wherein (a) an upper strip deflector (3)arranged above the rolled strip (10) with integrated fan-driven stripblowing (4) by means of a low-pressure nozzle (7) and with an upper rollbarrel gap seal (5) in the form of a slotted nozzle (6), and (b) aseparate exhaust device (16) arranged below the rolled strip (10) withan integrated lower strip deflector (17).
 2. Device in accordance withclaim 1, wherein the slotted nozzle (6) is designed in such a way thatthe seals the upper rolling zone (11) from the rolled strip (10) byexploiting the Coanda effect (flow of a gas jet along a curved surfacein front of a gas discharge orifice).
 3. Device in accordance with claim1, wherein the upper strip deflector (3) can be moved and is oriented atan angle of 20° to 45° to the rolled strip (10).
 4. Device in accordancewith claim 1, wherein the exhaust device (16) is designed in such a waythat the suction produces a well-defined flow around the edge of thestrip after the roll gap.
 5. Device in accordance with claim 4, whereinthe exhaust system is fan-driven through a suction tank (18) installedbelow the rolled strip (10).
 6. Device in accordance with claim 4,wherein the exhausting is accomplished with the aid of injector nozzles,which are installed below the rolled strip (10) in a strip guide tablein such a way that they can be turned on in zones.
 7. Device inaccordance with claim 1, wherein the upper strip deflector (3) and thelower exhaust device (16) form a strip channel (15), through which therolled strip (10) is guided after it emerges from the roll gap (12) andwhich is designed in such a way that is serves as a threading aid forthe leading end of the strip.